SET the best?

As with all amps, power supplies are critical to best performance. My custom built 300B monoblocks each use power supply one generally sees in stereo amp. Larger, better ps equals more filtering-resolving powers, reserves of power-transient, micro and macro dynamics. Add in some silver internal wiring, hand output transformers, no soft romantic old fashioned 300B sound. Actually nearly the equal of my 845 in most of impact related sound qualities. Hard to believe when you compare 845, 300B power supplies. 300B  power supply looks silly small in comparison to either of my 845's. Again, power tubes make large difference in SET, some romantic or old fashion sound, others modern sound, more linear.

I agree, SET will never be objectively best topology, just as any topology isn't. Each person has their own values as to what sounds best. Certainly, speaker choice is more limited vs higher power amps, although continually seeing introduction of more high efficiency speakers over time.

Mozartfan-

The “tube” in the AGD Audions contains the proprietary GaN output stage.

The glass envelope facilities heat disbursement and can be easily replaced with future improvement. 
The GaN module used is the only such chip developed specifically for Audio.

AGD has just come out with a stereo amp called the Tempo. It uses a aluminum chassis cut from a solid billet. It is a more conventional design without the “tube” but utilizing the same technology. I believe the price is $5400.

Thus it differs from any other GaN based amps. I believe my explanation is accurate.

The GaN module used is the only such chip developed specifically for Audio.

AGD has just come out with a stereo amp called the Tempo. It uses a aluminum chassis cut from a solid billet. It is a more conventional design without the “tube” but utilizing the same technology. I believe the price is $5400.

Thus it differs from any other GaN based amps. I believe my explanation is accurate.

@mglik Its not. The first sentence in the post above isn’t right. A ’GaN module’ isn’t a chip. Its a circuit board, likely with chips on it. And none of them are specifically designed for audio, although the module is, but its not the only module designed for audio.

The statement that it ’differs from any other GaN based amps’ is tricky. All GaN based amps are different, so technically the statement is true. But installing a GaN based module in an aluminum chassis is commonplace.

This is not to denigrate Alberto’s designs- far from it. He was involved with GaNFET manufacturing and knows how to use them very well. But no GaNFET is built specifically for audio.

Excuse the misuse of the word chip. Guess module is accurate.

And I am not saying that GaN technology is necessarily the best Class D.

Only that it currently seems to be a method that is quite popular.

My comment about Alberto’s module being specifically designed for Audio comes from the early review, believe it was Enjoy the Music. It pointed out that “all” other current GaN based amps use existing modules with chips that are currently used in non Audio devises like power chargers. Alberto’s design was focused on the use in his amps. This is my understanding. 

It pointed out that “all” other current GaN based amps use existing modules with chips that are currently used in non Audio devises like power chargers.

@mglik If he's getting semiconductor devices made for him I can see that happening. Usually you have to buy quite a lot of such devices to get any semiconductor manufacturer to pay attention to your order! But he might have an in with one of his former employers. But FWIW the chips used in switch mode power supplies have a lot in common with the requirements you face in building a class D amplifier.